Developing and validating a decision support tool for media selection to mitigate drainage waters

The nitrate nitrogen (NO3-N) and ammonium (NH4-N) and/or dissolved reactive phosphorus (DRP) load in drainage water from farms can be managed by reactive or biological media filters. The nutrient content of the drainage water can be obtained directly from water analysis, which immediately focuses attention on filter media selection. There are many factors that may be important before choosing a medium or media e.g. nutrient removal capacity, lifetime, hydraulic conductivity, the potential for “pollution swapping”, attenuation of non-target contaminants (e.g. pesticides, organic carbon, etc.), and local availability and transportation cost of media to site. In this study, a novel decision support tool (DST) was developed, which brought all these factors together in one place for five nutrient scenarios. A systematic literature review was conducted to create a database containing 75 media with an associated static scoring system across seven criteria (% of nutrient concentration reduction, removal of other pollutants, lifetime, hydraulic conductivity, negative externalities) and a dynamic scoring system across two criteria (delivery cost and availability). The DST was tested using case studies from Ireland, Belgium and USA with different agricultural practices and nutrient scenarios. It was then validated by SWOT (strength, weakness, opportunities and threats) analysis. The DST provided a rapid, easily modifiable screening of many media-based treatments for specific dual or single nutrient-based water drainage problems. This provides stakeholders (farmers/regulators/advisors) with a versatile, flexible and robust yet easy-to-understand framework to make informed choices on appropriate media-based mitigation measures according to users’ relevant technical, economic and logistical factors

Impact of P inputs on source-sink P dynamics of sediment along an agricultural ditch network

peer-reviewedPhosphorus (P) loss from intensive dairy farms is a pressure on water quality in agricultural catchments. At farm scale, P sources can enter in-field drains and open ditches, resulting in transfer along ditch networks and delivery into nearby streams. Open ditches could be a potential location for P mitigation if the right location was identified, depending on P sources entering the ditch and the source-sink dynamics at the sediment-water interface. The objective of this study was to identify the right location along a ditch to mitigate P losses on an intensive dairy farm. High spatial resolution grab samples for water quality, along with sediment and bankside samples, were collected along an open ditch network to characterise the P dynamics within the ditch. Phosphorus inputs to the ditch adversely affected water quality, and a step change in P concentrations (increase in mean dissolved reactive phosphorus (DRP) from 0.054 to 0.228 mg L−1) midway along the section of the ditch sampled, signalled the influence of a point source entering the ditch. Phosphorus inputs altered sediment P sorption properties as P accumulated along the length of the ditch. Accumulation of bankside and sediment labile extractable P, Mehlich 3 P (M3P) (from 13 to 97 mg kg−1) resulted in a decrease in P binding energies (k) to < 1 L mg−1 at downstream points and raised the equilibrium P concentrations (EPC0) from 0.07 to 4.61 mg L−1 along the ditch. The increase in EPC0 was in line with increasing dissolved and total P in water, demonstrating the role of sediment downstream in this ditch as a secondary source of P to water. Implementation of intervention measures are needed to both mitigate P loss and remediate sediment to restore the sink properties. In-ditch measures need to account for a physicochemical lag time before improvements in water quality will be observed

An integrated assessment of nitrogen source, transformation and fate within an intensive dairy system to inform management change

From an environmental perspective optimised dairy systems, which follow current regulations, still have low nitrogen (N) use efficiency, high N surplus (kg N ha-1) and enable ad-hoc delivery of direct and indirect reactive N losses to water and the atmosphere. The objective of the present study was to divide an intensive dairy farm into N attenuation capacity areas based on this ad-hoc delivery. Historical and current spatial and temporal multi-level datasets (stable isotope and dissolved gas) were combined and interpreted. Results showed that the farm had four distinct attenuation areas: high N attenuation: characterised by ammonium-N (NH4+-N) below 0.23 mg NH4+-N l-1 and nitrate (NO3--N) below 5.65 mg NO3--N l-1 in surface, drainage and groundwater, located on imperfectly to moderately-well drained soils with high denitrification potential and low nitrous oxide (N2O) emissions (av. 0.0032 mg N2O-N l-1); moderate N attenuation: characterised by low NO3--N concentration in drainage water but high N2O production (0.0317 mg N2O-N l-1) and denitrification potential lower than group 1 (av. δ15N-NO3-: 16.4‰, av. δ18O-NO3-: 9.2‰), on well to moderately drained soils; low N attenuation—area 1: characterised by high NO3--N (av. 6.90 mg NO3--N l-1) in drainage water from well to moderately-well drained soils, with low denitrification potential (av. δ15N-NO3-: 9.5‰, av. δ18O-NO3-: 5.9‰) and high N2O emissions (0.0319 mg N2O l-1); and low N attenuation—area 2: characterised by high NH4+-N (av. 3.93 mg NH4+-N l-1 and high N2O emissions (av. 0.0521 mg N2O l-1) from well to imperfectly drained soil. N loads on site should be moved away from low attenuation areas and emissions to air and water should be assessed

Global geologic map of asteroid (101955) Bennu indicates heterogeneous resurfacing in the past 500,000 years

Global geologic maps are useful tools for efficient interpretation of a planetary body, and they provide global context for the diversity and evolution of the surface. We used data acquired by the OSIRIS-REx spacecraft to create the first global geologic map of the near-Earth asteroid (101955) Bennu. As this is the first geologic map of a small, non-spherical, rubble-pile asteroid, we discuss the distinctive mapping challenges and best practices that may be useful for future exploration of similar asteroids, such as those to be visited with the Hera and Janus missions. By mapping on two centimeter-scale global image mosaics (2D projected space) and a centimeter-scale global shape model (3D space), we generated three input maps respectively describing Bennu's shape features, geologic features, and surface texture. Based on these input maps, we defined two geologic units: the Smooth Unit and the Rugged Unit. The units are differentiated primarily on the basis of surface texture, concentrations of boulders, and the distributions of lineaments, mass movement features, and craters. They are bounded by several scarps. The Rugged Unit contains abundant boulders and signs of recent mass movement. It also has fewer small (<20 m), putatively fresh craters than the Smooth Unit, suggesting that such craters have been erased in the former. Based on these geologic indicators, we infer that the Rugged Unit has the younger surface of the two. Differential crater size-frequency distributions and the distribution of the freshest craters suggest that both unit surfaces formed ~10–65 million years ago, when Bennu was located in the Main Asteroid Belt, and the Smooth Unit has not been significantly resurfaced in the past 2 million years. Meanwhile, the Rugged Unit has experienced resurfacing within the past ~500,000 years during Bennu's lifetime as a near-Earth asteroid. The geologic units are consistent with global diversity in slope, surface roughness, normal albedo, and thermal emission spectral characteristics. The site on Bennu where the OSIRIS-REx mission collected a regolith sample is located in the Smooth Unit, in a small crater nested within a larger one. So although the Smooth Unit is an older surface than the Rugged Unit, the impact-crater setting indicates that the material sampled was recently exposed. Several similarities are apparent between Bennu and asteroid (162173) Ryugu from a global geologic perspective, including two geologic units distinguishable by variations in the number density of boulders, as well as in other datasets such as brightness

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.Comment: 16 pages, RevTe